Semi-mechanical telephone-exchange system.



P. R. MGBERTY.

u SEMI-MECHANICAL TELEPHONE EXCHANGE SYSTEM.

AAPPLXCATION FILED JULY30,1909.

Patented JmL-12, 1915.

-e SHEETS-sum1 1:". R. MCBERTY. SEMI-MECHANICAL TELEPHONE EXCHANGE SYSTEM.

APPLICATION YXLED JUL" 30.1909. 1 ,124,488, Patented Jan. 12, 1915.

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i have/2501i' fa/f /0 L/Z SEM-MEC Patented J an. 12, 191D.

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.lok vim. MSCS www .w E355 is WH ,tw Q2u@ @Klik F. R. MCBERTY. HANIGAL TELEPHONE EXCHANGE SYSTEM.

SEMI-MEC `APPLIGATOII YILED JULY 30. WOL

Patented Jau 12, 191i y P. R. MGBERTY. SEMI-MECHANICAL TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JULY 80, 1909.

Patented Jan. 12, 1915.

6 SHEETS-*SHEET 6.

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UNITED STATES PATENT OFFICE.

FRANK R. MCBERTY, OF NEW ROCHELLE` NEW YORK. ASSIGNOR TO WESTERN ELEC- TRIC COMPANY, OF CHICAGO. ILLIN OIS. A CORPORATION 0F ILLINOIS.

SEMI-MECHANICAL TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Jan. 12, 1915.

Application iiled July 30, 1909. Serial No. 510,396.

To f//l whom. it may Concern lle it known that I, FRANK R, citizen ot' the United States. residing at Non' Rochel le in the county of VeStchest/cr and State of New York, have invented a certain ne\\- and useful Improvement in SemiMechanical Telephone-Exchange Systems. of which the following is a full. clear, concise. and exact description.

This invention relates to automatic srfitrhing systems `for telephone exchanges, and has reference more particularly to improved sending apparatus by `which the automatic action of selective line switching mechanism mar be effected and controlled.

A semi-mechanical telephone exchange sv-xem to which the present invention is especially applicable involves apparatus where-bv an operator at a central ollice may cause any calling line to be automatically switched into connection with -iny line Wanted. by actuating a key or combination of keys designating such wanted line. The extension of the circuit to the line wanted is acmmplished by mechanical switching appliances or automatic selectors which are governed by automatic sending or controlling apparatus, the action of which is brought about and determined'by the actuated keys. A number of connecting circuits ma).v be provided for each operator to use in answering calls. each connecting circuit having at one end means for uniting it with a calling line. and terminating at the other end-in a mecl'ianical selector switch. The sending apparatus may be brought into temporary associationwith any connecting circuit to control thc selector switch or switches through which the circuit is successively extended in establishing the desired connection. 1When connection is completed to the line minted. the sending apparatus is automatically disconnected and becomes immediately mailable for use with another connecting circuit. l

\n v suitable means may be provided in such a system i'or bringing a calling sub- .si-riberinto telephonie communication with an operator at the central oiiice and for uniting his line with the iirst of the series ol autcanatic selector switches to be controlled b v the operator in establishing the desired connection. For example, each line Molinari,c

may have an answering jack and line signal, as in the manual system, appearing before the operator who attends to the calls from such line, the operators connecting circuit in such case terminating in an answering plug which will be inserted in the springjack of the calling line in the .usual way. The operator after bringing her telephone (associated with the connecting circuit) `into service and learning the number ot' the subscriber wanted, VWill register this number on a bank of keys similar to those of an adding machine, by depressing keys representing the digits of the number. The sending apparatus will thereby be brought into service and will operate in a distinctive manner accordinp` t0 the particula r keys actuated. bringing about a succession of circuit-changing operations which will causo thc selective line-switching mechanisrn to extend the circuit to the line so designated.

The sending apparatus includes as one of its principal elements a point-finder apparatus comprising a series of contact points or terminals adapted to be selected by corresponding kejvs, and a finder brush arranged to travel over these contacts in sequence and to coperate with any selected point to cause the inder to be stopped at ed by the particular key in 'question and stop there.

In accordance with the present invention, the finden' after reaching the selected point is caused to travel to another stopping point, and the extent of travel required in this latter journey measures the extent of operation of a selecting mechanism and so determines a selection corresponding to, the key. The first stage of operation of the point-finder apparatus, in reaching the point selected by the key, may be termed its registering action, and the second stage lnaybe termed its sending action. The registering action will take place independent of the selector yto be controlled, but in the sending operation the selector and the finder may be caused to operate in unison, as by pulsations of current corresponding to gub is required lli me; and l wfiv: apparatus nl@y www@ ilus wir m View mtnfft brush. l new Uf lu: semm IL ulwffi'wzfal counQe-m tlm-willi, U2U-1l i brushes m1 il air pvwls in u .llrwim; m *Lhrnw their fmwuwl m' cumul-, wml# wulvfimll". Tlm lniwlm uw vlvcttlfully Jollnwmi in wig of threw. im! ouch sur mutually lnlclmcl agznit il@ thrmt of the sp1-mg tongues 5 l, 55, 56, by a Catch 57 which is normally held in the path of movement of the. rear ends of Said ba'ushes. As shown, the catches 57 are insu l hating bars mounted on spring latch-arms which are the free ends or tongues ot a sprinpA metal plate 59 fixed to the rotarvY frame 60.

ln order to bring any of" brushes into position to engage the contacts over which they travel, they must he released by trip-- ing the correspondiup7 catch to allow the brushes to be rocked upon their pivots by their springs 5l. 3o. '.lhis tripping of the brushes is accomplished by a trip-bar 64 which is pivotally mounted on an axis G5 and has at its edge a series of projecting lugs (lo in position to be moved into the paths ot the respective latch-arms when the trip bar is rocked ou its axis. It is intended that only one of the several sets of brushes shall be selected and tripped in. a given operation. and the trip-bar is therefor inclined at an angle so that the. tripping lugs; or will face positions successively reached in the rotation ot the bruslrcarrier frame. The trip-bar will he actuated to thrust forward its tri'pping lugs only for a moment when the end of the latchsarm controlling the desired set of brushes reaches an angular position justin advance of that occupied b v the particular lug which is at the proper height to en gage that arm. The movement ot the tripber may he accomplished by a trippinganagnet 6T thc movable armature US vvhereot" is mechanically connected to said bar.

Afsegmental metallic platt` T0 is mounted in position to be engaged by the contact ends of the. brushes as they are` tripped, this plate extending to the end of the trip range that is, through the arc traversed b v the brushes as one set after another throughout the series is brought into position to be tripped. At the end of the trip range the baril: of line terminals (il. (r2. ti. begins. These terminals are arranged in sets ot three, corresponding in relative positions to the relative positions ot the brushes by which they are to be traversed, and the diti'crent sets are arranged in an arc in position to be. slmcessively reached in a point-topoint rotary advance ofthe brushes.

To restore the brushes to their hitched positionwlicn the selector returns to normal, an insulating bar tio is a rra ngzed to be passed over by the brushes in their return liourney, the brushes in Vpassing over this bar being raised thereby against the tension otl their springs, until their beveled rear ends slip over the catches 57.

The motor mechanism for rotating the brush carrier frame may he as follows: An iron plate 73 is mounted to rotate with the shaft 50. but in such a manner that it may be given a fiat-wise or tilting movement into engagement with one or the other ot two iron drivingf rollers 74. 75. which are, located 0n either side of its axis and are constantlv driven bi shaft T6. An electromagiict TT,

which l tei-in the power-magnet, is arranged t0 magnetize the driving rollers 74 and 75 to cause them to attract. the iron plate 73. Said plate provided with cam surfaces, s0 that in the normal position of the apparatus the surface on one side ot the axis 5() will be closer to the driving wheel 75 than the sur i'ace on the other side of said axis is to the dri ving,Y wheel Tl. Normally, therefore, when the power-magnet is excited the plate Ti will be drawn into engagement with roller T5 to receive motion therefrom, and the carrier shaft 5t) will be rotated in a direction to advance the brushes. After the brushes have been advanced the distance required to bring them into engagement with ya given set of terminals. the power-magnet will be dcncrgized. the plate 73 will be re- 4leased from its env'affement with drivin roller T3. and said plate will recover from its tilted position b v the action of a spring washer T8. The cani surfaces of the plate beingr now angularly displaced from the axis of the driving rollers. the body portion of the platt` will be nearer to the return roller Tel which is of larger diameter than the roller T5. .so that when the power-mag` net is again energized the plate will be enn gagged by roller Trl. and the shaft'y fit) will be rotated thereby in a direction to return the rotary` carrier to normal position. A cani Sil is carried b v the rotar)Y element of the. selector to operate a switch spring Sl. On the tiret rotaryv movement. and while the brushes are passing the trip range, the cam forces said spring ril against an anvil S2. and at the end ovl' the trip range the cam allows the sprin- T 8l to recede from Contact 312 and enrale, thc alternate anvil 83. A

ci l malie-and-'brealt contact device or interrupter is also arranged to be operated as the lnush-carrier ot the selector' rotates. As shown. an interrripter arm 8i is pivoted in the carrier-trame similarly to the brushes 5l. 52, SH3. and carries at its forward end a roller .h5 which is adapted to travel over a toothed segment thereby causingr the arm to vibrate. .'51s the roller rides up on each tooth it rocks the arm X4 in a direction to close a contact 8o, ST. and this contact remains closed until the roller has passed over the tooth and has nearly reached. the bottom ot' the following;l notch. The brushes 51. 52, .725. are electrically connected in multiple sets bv the terminal plates il. 42. Ytil.y the plate 41 having tongues 5l makinlg contact with all the brushes 51. the plate l2 having,r tongues making! contact with all the brushes 52, and plate l hav ing tongues Titi making contact with all tlu` brushes 53. i

By the operation of the selector', the conductors connected to the plates 41, 42 and 43 may be connected respectively to any set of three stationa ry line terminals in any horizontal level, by first tripping the multiple lao whe which travels over the required i d tl'ien causing 4the brush Currier t0 `l the selected brushes reach the oi" le: rninzils in that level. purticnhtr system shown in the lector intended thus to l.. :i hundred sets of terminals, termin. in each set, for f. conductors und the test con A? re ieviirelyr` et u telephone circuit. 'ffl-*rior i'l then-lore be considered te thirty l;.\rn-:he:-. ien sets ot' three euch, ind three hundred stationary terminals urranged in ten levels corresponding to the ten sets ol' b1 hes, will ten vertical rows of three te Y. eneh in euclnlevel, or ten civ ol' thirty terminals each in all. For simplicity in the diagram, there are sin-fun onlyv two sels et brushes und a few oi the Contact terminals in the two correspending lere 1 defi/927115; appt/wtwfwfihe sending appuiw i izi'ii'itrolling the selective operations includes s benk of keys adapted to be actie :will s the operator. said keys being nr` f l epnrnle sets c :orresponding to the dineren?. ngits of linenumbers of the systern "ll .fiiiple exehunge chosen for illusii'ntion de ignoti lor/,i000 lines, and the hunk ol' keys shown therefore comprises at ser. oi Lliinidredjt keys. :i set ot tens" keys :mtl set ot units keys, euch set consisting oi ten keys numbered from to 9 inclusive. linen key in u set or tow, as shown diagram in illy in Fig. l, is arranged when depiessed to close u Contact controlling a circuit individual to the keys, and also to close :mother contact controlling :i circuit comnzon to lili the keys of the row. Means are ,:mrided for registering or LLstoring up"7 the number indicated by :my combination of keys eetuntech sind for using this number as :i basis for governing a series of selectin operations; Erich key is adapted to be held in its denressed position until the registers shown l LV.nimmtir-.ally in Fig. 2 and in ril in Figs. 8 to lt take up the number in irait/edv` by moving their respective p0intfinders to the. points selected by the corn responding keys. When the number indicated so registered the keys may be automstieelly released. As shown, euch key has e plunger Tilfli for actuating a set of contacts ;l and the means shown for locking the plunge 'fi in their depressed positions is a magnet l G9 haring long pole-pieces extendin along under ell the keys of ay set and adapte to engage urnnitures 103v which are carried on the plungers of individual keys and are ar ranged to be moved into Contact with said pole-pieces when the keys are depressed. The magnet when energized is not strong enough to drew down a key from its normal position, but is strong enough to hold fest the armature of any depressed key, and so to .vr the lock such key in its depressed position. The keys may be provided 'with the usuel springs (not shown) for restoring them lo nornn-l position when the retaining magnet dig energized. 7

The number indicated by @he depreswd keys und stored up" on the yAsie n, the distinctive positions rw 'which their respec-v tive pointdinde 'sneed "vill he mede the basis of co oihng sie it solei-ting operations; und in the gir'. the registers aire intended lo im si: is; controlling Steppers to operate in unison with the tant selectors und thereby determine the lections eeeording to the niunbers which tney have previously registered The sending apparatus also includes sequentie x'iieh mechanism by which diileren. .leviers or circuits are brought into ce one zitter another as the operation progresses. S5

.ller/zamen?. of registers? controlling step pcm and sequence sirchesfM-lhe device shown in detail in Figs. El to .l combines the functions of n register. te take up the num ber indicztted, by one oi' the of a, set5 and ot n eontroiling stepper to operate at :t subsequent stnge in un'on with :i selector to control the selecting operation, according to the number registered. It :also einl;odies the same mechanical principle the sequence switch, in that n single electromagnetic niotor mechanism operates nunaber o t' switches in any desired sequence. the di ilerent switching operations being successir l`; performed as the rotary element` successively reaches ditlerent positions in iis advance.

The rotary element EN@ of the in ei'tlninisin shown x vel-tieni shalt carrying :it its upper end zi tiinlerbrush or wiper 201 adopt ed :is the shui't rotates to tru vel over und ineke contact successively with stationary terminals 202.

In the .torni shown the brush isndapted to break contact with euch terminzil before making cfnituct with the next. Connection muy he. nitide to the ino'v'ing U0 brush Ql by means ot :i stationery brush 207 bearing on it siipiing ll carried hy the rotary element. seid slip-ring being eleci tricitlly connected, with the metallic niountf ing oli' said brush 20E. lflleren stationery tern'iinuls :tre shown, arranged :it equi-distant points around a circle; und the inechzr nism is adapted to allow the brush :o stop either upon any of suid terminals, or upon intermediate points between suid terminals. There ire thus twentystrfo positions l or hnlfssteps for the rotary eli-ment, indi cated in the diugrrmn Fig. :2, oiE which posi tion No. 2L ,vill be imnsidered :is immuni. A inormneni ot the finder from one position to the next. is trou: fi terminul to the 'hilo 'ing insulating4 segun-nn will he considered as ai half-step. :i Vfull step lu infrl :i inmieinent freni terminal to tei nml.

.Preferably s constantly'driven "mwen 139 shaft is'arranged to be mechanically coupled to drive the rotary element of the register, through the agency ot magneticallycont'rolled clutch mechanism. Thus, as shown, the rotary element carries an iron disk 203 which serves as a rotary pole-piece. so tospeak.y for a clutch-magnet or motorinagnet 2013; and an iron frictionedriving disk 204 carried by a constantlya'otating shaft 20F is adapted to be drawn into ehgagelnent with the disk 203 when and while the motor magnet 20G excited. The rotary elei'nent carries a series of cams 209, 210, Zll. for actuating switches "213,214,215, respectively. as shown most clearly in the diagram Fig. 2. The cam '205) is adapted to hohl the spring 213 away from the Contact anvil 216 except in the normal position (Q2) when said contact is allowed to close. Cam '210 holds spring 2li away from both its alternate contacts 217 and 21S in the normal position, which in this case is No. 22, and also in position l.y but is adapted to cause the. spring to engage contact 218 in the even numbered positions :2. 4, 6, etc., up to and including 20. and to engage contact 217 in the intermediate or odd numbered positions 3. 5, 7, etc., up to and including 2l. ln the positions having even numbers the traveling brush 201 rests on terminals, and in the intermediate or odd-numbered positions the brush .01 rests on insulation between terminals. The cam 211 operating the switch 215 is for the purpose of closing a local circuit 'for the power-magnet 206 while the rotary element is in transit from one position to the next. to insure ,that said element may come to rest accurately at any position. Said cam 211 is adapted thereiore to cause the switch lever 215 to engage contact 220 between each position `and the next. and to break such contact as each posi Lion is reached. The pivoted switch lever 2': 3 carries a roller .210 which rides over the te-th ot the cam `.211. and a fpring 2521 acting upon the lever 215 causes the roller in descending the slope of each tooth to push the cam slightly, so that-,after the power is cut otl the roller continues to push in until it reaches the bottom of the notch between two teeth. thus insuring the accurate positioning ot' the rotary element. lt l'will be understood that this arrangement of camsr and contacts appliesl only to the particular" i'orm of mechanism intended tor operation with the particular circuit arrangement shown m Fig. il.

The sequence switches which are indicated diagranunatically in Figs. i and 5 are precisely similar in mechanical construction to the combined registri'. stepper and switch shonn "n FigsA -'-l l. except that they will no1 be provided with the inder-brush QQl, and the stationary contacts 202, but will have instead a large number of cams and switches. arranged to perform the more numerous successive switching operations hereafter to be described.

For clearness in the diagrams, the switch springs of the sequence-switches of Figs. 3, 4 and 5 are not shown in actual relations, but are so located as to give the clearest arrangement of circuits, and the operating cams are also omitted, the positions of the rotary element in which contacts are closed being indicated by the numbers placed adjacent to such contacts. F or example, contact 409 (Fig. 4) is closed in the first, second and thirteenth positions. and this is indicated by the numbers l, 2, 1.3, adjacent thereto. Each sequence switch, however, has a switch,- lc\ er corresponding in function to the switch lever 215 of the mechanism before describedthat is, for the purpose of closing a local circuit for its motor magnet between the regular positions, and in the diagram those switches are distinguished by being shown as some-- what heavier' than the ordinary switchsprings, and as having a. cam roller. The.

'numbers appearing adjacent to each such switch-lever upon the opposite side from its contact. indicate that the switch is open in the positions so numbered and closed in all other positions. That is to say, in Fi 4,

for eXample,/the numbers 1, 3, 4, 5.76, g, 8, 13, 14, l5, indicate that the local switch is open in the first position. closed between the first and third. open in the third, closed between the third and fourth, and so on. Where the numbers applied to the local switch are not consecutive, as, l, 3, 4, etc., for example, it is thus indicated that while theI local switch is onen in the positions named, it is closed continuously between such positions. Thus when the device leaves the first position it will be carried through to the third. without a. stop, due to suoli continuous closure of the local circuit for its motor magnet.

Operation of system-A further detailed description of the apparatus used in the sys tem, and a statement of the electrical conn tions of each part will be unnecessary, as d `vices of known types arc indicated by the usual conventional symbols, and the electri- /cal connections are clearly shown in the diagram. Certain of the usual appliances re` quire in an actual telephone system, such. for example, as the operators telephone set, have not been shown because their connections-and manner of use will be Well understood by those skilled in the art, and to show them in detail would too greatly complicate the diagram. Several batteries are shown, and for convenience in tracing circuits are designated b v different reference characters. but it will be understood that in practice a single central battery would be employed, connected as indicated. rThe organization and mode of operation of the system can that the sequence-switch advances to its third position without stopping. At the seeond position a contact 411 is closed, conA trolling a common branch from the super- \isory signal lamps 412 and 413 which are thus brought into service, under the control ot' the usual supervisory relays 114 and 415 respectl 'ely. As the sequenceswitch of the t selector reaches the third osition it clos a contact 116 which conip etes a circuler for a relay 80() (Fig. 3)' which governs the seizure of the sending apparatus by the connecting circuit which has been pnt into use. rl`his circuit is traced from battery ll through the sender-seizing relay 300 to conductor 118 which is multiplied to the contacts e116 of the sequence-switchcs ot all the connecting circuits of an operatons position, the circuit heing completed through the contart 416 ot' the one which has heen taken for use` to earth.. .\t the saine time a con tact 41T is closed which extends a circuit -llt for the scqucnceswitch inotor magnet i? to the sending apparatus, to he com plcti-d at contact 303 of the scruience switch associated with said sending apparatus when said lastsinentioned sequence-switch reaches its third position. This will he whenall the registers have taken their ositions in response to the depression o the keys.

The circuit 418 controlled at Contact 416 furnishes a means hy which the sequtii'icen switch ot' the sending apparatus can be controlled hy any connecting circuit; and the circuit lll? controlled at contact 303 of the sequence-Snitch associated with the sending apparatus furnishes a means whereby the sending apparatus may exercise a reciprocal control over the sequence switch of the first selector. When the relay $300 is excited, a circuit is closed for the motor magnet 31T of the sender setpienoe-switch7 which there upon mores to its second position. The op erator having now communicated with the calling subscriber and learned the number of the line wanted, depresses keys (Fig. l) representing the digits of such number. For example, if line U50 nere called, the operator would depress the hundreds key No. i). thil tens key o. .'i, and the units key No. 0. As shown in Fig. i, there is a register for each .set of lofts, that is. a hundreds register. a tens register and a units registerv` the construction of which has heretofore heen described. The keys in each set are adapted to selectl points in reverse order upon the register corresponding to such setA In the case assumed the hundreds key No. l) will ground the terminal at position No. .2 of the hundreds register` so that the pointfinder of said register. after reaching the terminal so selected hy the hundreds key No. t) will take ten full stops from terminal to terminal in continuing its journey around to the starting point or normal position No. The tens key No. will ground the termina] at position No. 10 of the tenslregister, so that the point-finder of said register, after reaching the terminal so grounded, will have to take six full steps to reach norinal. The units key No. 0 will ground the terminal at position No. of the units register., so thatithe point-finder of said units register upon arriving at said position No. 20 will have to take one full step farther to reach normal. ln other words, each key will select a point distant from the final stopping point a number of fullA steps cor responding to the numeral olf the key, plus one.

When a hundreds key (for example, key No. 9) is depressed, a circuit may he traced troni the battery 205 (Fig. Q) through the motor magnet 206 of the hundreds register hack contact of thender relay 226 thereof, conductor 227, through contact 304 of the sender sequenceswitch to conductor 10ft, and thence to ground at the closed Contact 106 of the depressed hundreds keyu The motor magnet 206 of the hundreds register being thus excited moves the teint-finder of said register until the brushlZOl reaches the pointgrounded by the depressed. hundreds key, in this case the terminal at position No. Q, whereupon a circliit is com pleted troni battery 228, through relai. 226 of the hundreds register, to the finder irush 201 and the terminal on which said brush rests, and so to ground at the depressed hundreds key. Similarly, any tens key when depressed closes a circuit which may he readily traced for the niotor magnet of the tens register, which circuit is opened hy the finder relay of said register when the point selected hy such key is reached by the teus finder nrslL Likewise, any units key when depressed closes a circuit for the motor magnet of the units register, which circuit is opened hy the finder relay thereof when the point selected hy such Ikey is reached hy the units finder brush.

'The relay 22o in attracting its` armature, hrealts the circuit previously traced for the motor magnet 204i and connects the grounded wire 22T to a wire 2129 leading through a contact i505 of the Sender sequenceswitch to the motor magnet 31.7 of the ltf ter. wherehy said seqiieiiceswitoh is adranred to the third position. ln this position contacts Sitio and T are closed from the front and hack contacts respectively of the stepping relay 809m the alternate contacts of the "escapenient-`r switch spring 214 of the hundreds register. so that the step relay :1,05 may now control the sending nc tion of the register to advance its brush 201 from the point selected hy the key around to the normal Jposition No. 22. The intermittent action o the stepping relay l-U zillm "il" of lay 42() fat the first selector is released 'and opens its front contact, thus breaking' the short Circuit of the trip magnet G7 of said irst seleotor. The power magnet `77`is not released, however7 as it is held up by current from battery l125 flowing through said pou-ezinagnet 77 and trip magnet 67 in series, and through Contact 43() of the selector sequence-switch to earth o While the brush carrying frame o the selector continues to rotate, thtuefore7 the trip magnet Gi is excited and rocks the trip har (il to thrust the projecting lugs 6G into the paths of the latch arms the i brush carrier :trarne continues its travi.; the first latch arm to reach one ot' the tripping hun.: (36 will he engaged thereby. and detained suiicieutly to release the three lz'rush normally held by said latch arm, these brushes to he rocked upon their pivots by their springe 55, 56. and so thrust into contact withl the grounded metal plate 70. The partieular set of hrahes which is thus brought into service will depend upon the number of steps through which the selector had advanced hetero the trip mgnet was excited. in the raso assumed, wher-'e the hundreds; key No. l? was depressed. the register and selector U had taken teinlull steps in unison heiore the arrival of the l'xundreds register at its stopping point resulted in the opening ol' the stepping circuit and thc, energization of the trip magnet at the selector. ln these '5 ten steps the latch arms of the first nine sets of hrushes (counting from the bottom up.) had successively passed the points at which the".` might have been tripped, leaving the latch arm of the tenth set of brushes in po` .sition to he engaged by the projecting lug ol' the tri p bar as the selector continues to advance. In other words. the set of -iuuslu.\- which has heen tripped and hrought into -1erriee corresponds to the hundreds which was depressed. ln the present 2- the hundreds her No. @Amthat t 'lilith hund reds la'eyY caused the. '10th I het to he tripped and lutoi i i, he

on as the hruehes n'ule ront* *l iuoded metallio segn'ient 'l0 'the tot I yl2() is imn'iefliately excited again hr current llowinf troni buttery 4.2i througzli *ff* relay.. Contacts 422 and to i. and l in multiple, to the plate l ground. lThe test. relay in drawing ruit. oi the trip nmfluet. said trip u ingr ebwted onl)Y loner enough to as the lrusii oarrier .fehatt ot the `r i t llegan to rotate, the earn Sill) loved, the spring 8l against contarr anvil 9i. rfunplrting a circuit from battery 408 through motor magnet 4.07 of the sequenrearmature again closes the short cir-k switch, oohtact'432, contact 82, spring' 81,

to earth. The sequence-switch is thus advanced to theth position in which its motor magnet is connected through a contact 433 to the'alternate contact anvil 83 of the camr'IO actuated spring '81. The cam 80 is shaped so that when the'rotary'element of the selector has advanced all the brushes beyond Ethe trip range the spring 8l will' be allowed to engage Contact anvil 83, ,thus completing a circuit for the motor magnet of the seqiuxucoswiich, and causing said switch t0' he advanced to the 6th osition..

' in leaving the' '5th position the contact 423 loroken, out Contact 422 remains closed L80 the. circuit for the tripmagnet, thus opening the branch by which the power magnet was previously held up in series with the trip magnet, leaving said .power magnet opendmt for its excitation upon current erived from "the front Contact of the test relays which will now govern thefurther advance oi `the selector brushes in fhunting an idle trunk. The sequence-switch in reaching the 6th position also closes a Contact 484 by which its motor magnet 407 is connected to the hack. Contact of the test relay, so that when the test relay is denergized, :is itkvill he when an idle trunk isifound, the sequenceswiteh will he moved from Ythe 6th position to the l7th, in which the test relay will be 'cut olf and the sender leads 424 and 434 simtrip range and the beginning of the range.

containing the line terminals As 'the hrs'zshes pass'ofl the end ot the grounoed metal segment Y() the interruptor roller is passing over the long tooth 89. so that. the short circuit 427 is closed and the test relay maintained excited. is the brushes reach the First set tu terminals. however. the roller of the inierrupter enters the first noteh (in the particular rmi-rhino under consideraiion\ and the iuterru'oter Contact So. 87. is opened, wealiing tini short circuit` 127 and 'ing the test 420 dependent for its es* tation upon a ne iit which iufm' he cour p.. 'l through tl d test brush 53 of the .set which has been tripped to a test terminal GT3 which Wi ll he Connected to earth if the line tested is husy. All the sets ofline termi nale reached in the travel of a given .set nf "los Ybrushes are the terminals of trunk lines trunk line leadingr to a final selector of the group desired will be required to hunt over the. terminals of trunk lines representing final selectors of the desired group, until an idle trunk is found. The advance of a given set of brushes of the first selector over the line terminals in the corresponding level will therefore he a hunting operation. The brushes will stop upon any set of terminals only if a certain electrical condition exists at the test terminal of the set, such condition in the present case being the absence of a ground connection. As will hereafter be shown, the test terminals of all trunk lines which are busy will be connected to earth, and circuit will therefore be maintained for the test relay of the hunting selector through the test brush 53 to earth as long as the test brush is passing over the terminais of busy lines. As `the test brush reaches efch terminal thc circuit for the test relay 420 through the interrupter contact 86, 87, is broken; and as soon as the test terminal of an idle line is reached, there being no ground connection upon such test terminal, no circuit will exist for the test relay 420, and said relay will be released, breaking the circuit of the power magnet 77 and causing the selector brushes to come to rest upon the terminals of the line so tested and found idle. The test relay 420 in recovering also closesa circuit which may be traced from the battery 408, through the motor magnet 407 of the sequence-switch. contact 48e, and through the back contact of the test relay to earth. The sequence-switch is thus moved from the 6th to the 7th position, in which the circuits for the test relay and power magnet of the selector are open, and the sender leads 424 and 434A connected through contacts 436 and 43'( to the line brushes 51 and 52, respectively, and so to the conductors 501 and 502 of the trunk line leading to the final selector. Contacts 463 d 464 are also closed, connecting the test brush 53 to earth, and so establishing the grounded or busy condition for all the multiple terminals of the trunk line selected.

Returning now to a consideration of the sending apparatus, it will be remembered that when the. register, acting as a stepper or sender i reached its final stopping position No. 22, it closed a Contact Q16, completingr a circuit for the stop relay 309 which opened the stepping circuit and so caused the test relay at the first selector to be released and -the trip magnet to be excited. I-,he 'stepping circuit should be held open long enough for the selector lto travel through a distance sufficient to permit the tripping ot' a set of brushes. after which the stepping circuit should be closed at the sending end when the next selecting operation is to be performed.

For the purpose of holding the stepping Circuit open during the time necessary to trip a set of brushes, the timing controller or auxiliary ser{uencc-switch 320 is provided.l as shown in Fig. 3. The motor magnet. C515 of this timing controller is connected through the contact 313 of the main sender sequence-switch to the conduct-or 314 which is grounded at contact 216 when the hun`v dreds register reaches its final stopping point, so that .said motor magnet 315 is excited in multiple with the stop relay 309. The timing controller ai'ter lcaring its first or normal position runs through to the 7th position without a stop, and during the time required for this tra\ el the sequence-switch controlling the sender is maintained in the Lith position in which contact 31S controlling the stepping circuit opened. 'l`hc stepping circuit also held open at the back Contact of relay 309, which is maintained excited by a circuit closed at contact 336 of the timing controller while the latter is running from its 1st to its 7th position. As soon as the timing controller reached the second position the sender sequence-switch was moved from the 3rd to the 4th position, the circuit for this operation being traced from the battery 316, through the mctor magnet 31T of said sequence-switch, contact 313 thereof, contact 31S) of the timing controller, to earth. The sender se quence-switch is thus mored from the 3rd to the 4th position, closing contact 321, from which when the timing controller reaches its 7th position a circuit will be completed througlrccntact 329 of said timing control ler to earth, whereby the mctor magnet 3.17 will be again excited and the sender sequcnceswitch moi ed to the lith position, In this position the contact 323 is closed, whereby a circuit will be completed for the motor magnet 317 provided the tens and units reg isters have both performed their registering actions and taken up the positions selected by the depressed tous and units keys. This circuit may be traced from the battery 316, through motor magnet 317. contact 323. wire 324, through the front contacts of the finder relays of the tens and units registers in se- `ries, to conductor Q36, thence through a contact 325 of the sender sequence-switch, to a wire 337, through the contact 107 ol" the depressed units key, and Contact. 110 ot' the de pressed tens key to earth. The sender sequence-switch is thus moved trom the 5th to the 6th position. in which the stepping circuit is closed at the sender end at contact 327. In the 6th position the contacts lll) lol

unil 329 ure also closed. connecting the front unil hurl; conturts respertively of the stepping;r relay to the escapeinent contacts of the tens register.

The stepi'iing circuit inning heen hehl open for zi period of time measured hy the 'passage ol" the timing controller from the lst to thil Titi position to :illow time `for the tripping oi" the set oi" hriishes :it the seleitor. is now closed nt rontiirt 'l to await the nexty set of stepping impulses which will runsinittiiil fri-iii: the final selector. so: ii :is the liirnshrs ol the first. or come lo rest upon the terminals of .li lintr` lmiilingr to :in iilli liniil selector. tlm` stik rgiingf rir'ziit. is iistiililisliril as foll-:ws: l` 1a rr fitll nl; the linril selector. t l

l' lrough the inn rrlui.' .T30 thereof. to trunk im ro ilni'tor Sill leiiiling to tlnl terminal il nl' u trnnh' lint` :it the iirst` selector. to the lirnsp .il o? .mul srhirior. ronlziift Alfio.

sri'ler leinl lili. .sti-pping' rrlilv Tails, hurl.' ifolitwt ol' 110V 'r Y Chili. i" ntzirt 32T. soniler l 'l 434'.. tintin-t lo?. huish of the tint rim'. trunhr lino tviziiiiniil Vfl. triinli von .i r thriuluh nerim/illy elo z-.iiifiiut seigiif-zii'e \.uii,'li ii-s i iiited with i' e 3mi sehn-(or. to mirth. 'lln line relnV il ifi linul seh'iti-r iii'riispvnils in tunis uw test relu): 2li olv the liz',r` rele! tor. il hlx' urz-Ant in thil riaitnit linst i'rwiit i-ontfict n cirruil. ..l.fery 3. through the unter ningfi". norrniillr clos-vil ontairt 7M ol" the ,.i-iiiifiiclr-i'iitch :inil i'i'onironrirtol' the lint` i. ti'i to euah. Thi' epicuro switifh :is oiiziteil uitli the lniil :selector i: thu.k nioved o its sri'onil pifition. in uliirh u circuit yis hi nl Vroni liiittiiry :325. through power iriiiffzirt ii' ol' the tinzil selri'tor. rontiirt 52C it ihr. wipienifr \\\itrh. through the l'iont von .zii-t olA the luie relzrY fuif) to eiirth. The mower imigni-t living thu`v rxvitril. the liriish i i in ri lation. unil :is thi'A in- JB Wsw iiier it;` tootheil n it :mzlwf unil hriyrilv thi` rontin-t SV. seriioi. i 1,:il.ifhin;:ut eiiih `i iii-i uil` l'roin l iitit il. iinilnr. i` ll ihr uomini su itI h. hurl; lfilul olA the timl f' il'i I lr/ ilitrriuiplifr ironliiet Slt. i. limi, Akhor-t ririiiiiingij the line f tlifil stepping' :'ohrr 3tlg' :it the ii lui liiiniirg'i/e-l (wu-li linie siliil "lflt .it tho liizul ywh 'Ii r il low-il.

- vppiiig ffiruiiit first est-:ili-

tlie hnerilu):o'l`tl1eliniil wiping relu) S of the Ytopping remy 303 in ifiinzplrtrs u circuit vtrh infinit Sii for the JUV of tu tens register lili' he venin-nient coment 218 or" sziiil .mi nl V chr m11 is denergzed it completes at fts buck contact :t circuit for snid motor magnet of the tens register, through the sequenceswibch 329 und escapenient Contact 217 of the tens register. As the armature of the stepping rolny is Vibiettd the tens register is thus stepped around to its final stopping position of.. as already described with reference to the hundreds register, the `number of steps being:y dependent upon the particular tens key which was depressed. lYhen the teus register reaches its final stopping posh tion it closes its Contact 216, completing oirouit` through seqiienceswitth Contact :1 for the stop relay 300 of the sendo". its ln tore described in the operation of the huuilreils register. The stop relay 30'.) opens the stepping circuit. its before described. :intl muses u set of brushes to he tripped ut tln` tinul selector. The set of hriisries tripped vorresponds to the tens hey which hns heen depressed.

s the hrnsh Currier of the l'inill solertor lieju'ins to rotatie. the vani 8O ot' Suid linul lector i'fiiuses the Contact S2 to he closed. ronipletinir u oiri'uitl'or the niotor unignet T ot' the final seleiftor so(;i1eiees\\'iti.h. moving sniil .switch to the third position. This is the position in whii-.h u set of brushes rmi liitripped: :intl :is hil line riilnji im) is reloused when thel tens' rigiiter completiy its operation unil i'iiu es the stepping circuit to be opened bj.' relay Bill). ssiitl line relu) 55.*() in opening..r its front Contact hreiilis` the short Circuit ol the trip niugnet, lesivinfr the power magnet und trip ning-net connected ir series in :l circuit which may he triirid Vtroni buttery 525 through the power nnnlinet TT unil trip magnet G7 of the final seleitor. to rontiict 530 of the seipience-switch. unil throiig'h the hurl' Contact Bill ot' ii poliirizeil hns-i' test rehiiY i0 to earth. The operation olv tripiliinir the hrushes is thi` siinnl :is pre- \ioil.\ iliiffvrihiiil \\it'h referinri to thil lir t swlwior. :intl when he test hrush of thiA set uhii-li is' trippiil` uraltes rontiirli proiunliiii nietirllii segment itl ol' thVH si tor :i riroiiit. i coinphtf'il l'oi' the line r INU through ooiitiiift 5f' olithe :-eiiiiir'- srvitrh. lotlir test hrnsh l. seggnunt i'fl.

urtli Thi.` sliort. ':irruil: the portion 1. 'rino limiting lmoli to the r-eiiiler. unil tlsi; ii rohr.V living' :rluin energimil. sliint-veireuitrA thiA trip nniifnet (ST of they selector.

A\s thilirilshes lenve the segment Til ut'. the

end ot' ihr,I trip range. unil enter upon the.

lector, whereby said switch is moved from the 3rd to the 4th position. In this position the trip inagnt is nermaimntly cut ont nl? circuit hy tln-l opening of nonllact $330.

In thu final selector, the Segment SR is proriilwl with an @Xtra notch in adranie of tlny notfiflios cmrnSynniling t0 this pnsitinfiri ii. ffliirh thv lirnglwsront nimn tlm lint* terminals. S th@l intvrrnntnr rnllwf S nl tln final Soleu'or passt-,s ilnwn lrnni thel lungi tooth intr this lint not/fh in thi "linv lierininal rangv" in :uli anni" ni tlm nnlil'ws infn rrsfiintingf linv-unnnvcting in "inn thi limi ircnit mntrollwl lrr inlfrrngiur cnn tart Hl? is lirnlirn, :unl thfI iiirl, Ui tir' naw sri-iw: nl wlvrlingr inni/ninos is applird to the riipiinf rvlay f at tlw rnihsix Tin ping Cirrni rfliivli \\';.i.-t nprnnil :it lli@ sri'nlr wlwn tlw te-ns rrygilsr wfniiilfatwfl it Onnr ation i5 (rinsed again hallar, tin. lirrit nl" the nnit4 sclrrtingr ininnlses. if; applisfd aj, tin: linal @ttor at tlm Linnl the intnrrsptor rollt-r S5 enters the [iran or prnliininary notch in th@ lino, runnin. Tlw sti-miingj Jirfnit was lnilf'l upon :it tlm ,fvntlur during,r the imeiratinn 0i' the timing ni'nitrnllwf, nliiln tin: Iirnsliffs zit' thu Hrlector www; lwinff trippccl. Wlrrn the Lens rrgihtrr cmnplrtri its opor- :ltion it ranSOd thv Stm.) rvlny 309 tn be CX Cited in multipla. with tlm timingr wntriiillsr l 15 which nilvuncocl from its Ttli to its 13th positiorn holdingr tlm stop rfhrv 309 excited hy a Circuit i'rnni liattrrj.' Fill,y through said Stop relay 309 t0 conductor Sli/f.y :ind tlirnugh wntact 331/5 of the tin'iin,gr Controller to earth. The timing controllnr in reaching its Sth position (flows a cirrnit for the nntor ning* nvt 31'( nf the Svnfler :swnir-nCr-fswitrli. whereby tlm latter is ntli'fanffil lrnni its; {Sth to its 7th posities lrrmiliinp; lin: rircnits: lwtwvon the tuntxicts of thc, stepping: r'-lny and. the register ay'ipuratns. Then tln timing; controller rcarh its 13th pnritifln tlm cir- C-nif, iS again Cmnplvtsd nr theA nmtnr ning not of the Sender Snr;nenrus\\'ituli, through Contacts l and Zfi advancing' the qunncvfenituli to its; Sill pnaitioin in which the front and back' Contacts 0l tlnf teiv'rgiing relay are Connoctctl through cmitacts 83S and S7335) resmectirely, of thil Seinlnr sifqncnceswitch to the cscapimcn writarts and 217. respectivnly, 0i the n'rits rrgistcr. The Stop relay 309 is denergi'l'cd when the L ing controller reaches its 13th position in which Contact 336 is opened. The sending apparatus is now reachY to receive the gecond or units set of selecting iinpnlsr from the i'inal selectiz Thi? irSt or prvliiiinaiy iin-- pulse which is applivd tn the Stepping; relay :it the Linie the inl'nrrupter rnllifr nnte the first notch prcliiniziaryV to thi; lino ri Causes the Stepping relay tu cnnnilrif at front Contact a Circnit rnni Qimini. thym tl'irmijfh the newer magnet (if said regni-z' to the free, pole of battery i250.

Tn the :ase assinncd, where nnitgl key No 0 was delires ed, the finder brush of tlm nuits register came t0 rest in pofzitinn Nn. 20, so that said nuits register wili nov; be moved, :la thu srpping relay rccvivca ii, piriniinaifiY iin1nilsf\-1n position NU. 2l. Nnw an the interrupt@ roller i5 at, tls final selctnr l ws thv preliminary i notch and np nn the next tooth. Closing @intact fw?, n", :mil short circnitinff the lino ilu i wlmi $05 inning Llrmfr i mi, i a buck nonast a rirsnitf'ir ihr n'mtm i QUJ nl the, units iufxtrr. l en minuit Contact 217 and i, nenffrafwit-'i (winni-ut 33S), rflwrrliy the uint rpg-inter Hinwil to ils iinsil ftniliping privation No in rlilinr a circuit i'nr th@ :iop inlay Zfi (inw tin-(nigh sifqiieiicws. trli contact rfe in t il, @top rela? 305:) to 0pm ih@` #um 'h irrng. Non a5 the ii'iturrnntor rulli-r r5.3 :it in@ final Frhwftnr rnrr tin? fnl lon inn' ni'nfli. rfnrmmntiingr n n pntiivn of tlin fri'fctor l i, 'v01-tival nriiblicr upon the ii mw (fi lineV lifrnilnal lie slinit. circuit WET ('mitrnllml :it ihn inmrnptnr contant, 1%', limiten; :incl :is thvv line i mining' cirfnlt noir lirnlin at i iff Standen: tl n lintA i r will br (loiiiinrgizoiil. and in rr-ifm'ering 'will @non the circuit of tlie pnwr magnut enntrnllfcl at the frnnt imitant rif irl inlay, \,rlicr0bjr ln: tripped of Solvntinf brnszlis will be brought in rmt upon llnj fire line tl'ri'ininals in tlv: prcrinmlr iflimrn Inns vrel The first mit of lim: tfnniinalef this: Glimmen roi'rf-,Spnii-:ls t@ ihr, iirt units; kw: F0. (l Whirl. was flvprvssed At the cnil ni" the hat ninl'nr control nl the units r@ tru smiling urination.;

lin whip fi nn "fr uur 50ntact SiS liernnf.r Contact 315) nf til-e timing; mntrollxu to eartlr The sefnrncn-swifili is thus moved tn the 9th pn'mitiun. .Vlwn tlrf timing controller reaches its first nnsition the motor magnet of the sender sequence- .micli is; again excitd in a. vircnit through cnntart 321 of. said :Switch an contant 3i? thv tiA iing contrnllnr to Panfili.

nier imi; the the '.tr. and 1; ing the 9th. pusilinn thi l i-al switch Contact Si.) is cl fl lit ist wisitni xirongirto tlm 1st or norma i, in i3- il@ "nu VH plant, in il., r .1, ,.i n Vi/nen the sender sequemewsv" liti mensa the 9thl position the contact 346 isl opened, breakingl the circuit for the locking magnets 102 of the keys (Fig. 1)' whereby said keys are released and allowed to return to their normal positions. As the sequence switch reaches its 9th position it closes contact 308 and completes a circuit which may be traced from battery 408 (Fig. 4) through motor magnet 407 of the sequence-switch associated With the first selector, contact 417 thereof, Wire 419, Contact 303, to earth. The sequence-switch ofthe first selector is therefor moved from its 7 th to its 8th position, in Which contacts 436 and 437 are open, disconnecting the sender leads 424 and 434 from the first selector. Contacts 461 and 462 are closed in the 8th position of the first selector sequence-switch. connecting the link conductors of the cord circuit through to the brushes 51 and 53 of the first selector, and so through the trunk line conductors 501. and 502 to the final selector.

As the sequence-switch of the first selector leaves its 7th position the Contact 416 is opened, breaking the circuit f'or the senderu controlling relay 300 (Fig. 3) which is released. The sending apparatus is new completely restored to normal condition, all circuits being open between the registers and the sender sequence-switch, and contacts 327 and 310 controlling the stepping circuit be ing also open.

When the line relay 520 of the final selector is released at the end of the final sending operation, a circuit is Iclosed from battery 506, through the motor magnet 507 of the final selector sequence-switch, Contact 584 of said sequence-switch, back Contact of the line relay, to earth; whereby the sequence-switch is moved to the 5th position. In this position the busy test of the called line is made. Vhen the test brush of the final selector comes to rest upon the terminal of the called line, a test circuit is completed from the test terminal of said line to the test brush of the selector. and through coutact 552 of the sequence-switch, windings 553 and 554 of the polarized test relay 550 and contact 555 of the sequence-.switch` to earth. The test relay is marginal in its operation. It is adjusted to attract its armature upon current received from the test terminal of a line that is free, but will not respond to current received from the test ter-- minal of a line that is busy, the test relay in the latter case being shunted by a path from the test terminal of a busy line-to earth at the already-existing connection.

As the final selector sequenceswitch reaches the 5th position. a circuit vill be completed for its motor magnet, whereby said sequence-switch will be advanced'to the 9th or busy-back position, at which it will stop, if the line tested is busy, but if the line tested is free a circuit will be maintained for the motor magnet of the sequence-switch until the 0th or busyback position has been passed; lf the 'line tested is busy the circuit for the motor magnet will be from battery 500, through said motor magnet 507, Contact 541 of the sequenceewitch, and back Contact 551 of the test relay to earth. The contact 541 is maintained from the 5th to the 8th position. and the local contact 510- is also closed between the 5th and 9th positions, so that the sequence-switch will in any event reach the 9th position. In this position the free pole of the busy tone interrupter 500 is connected through contact 542 of the sequence-'switch to the trunk conductor 502. The circuit is thus intermittently completed fromv the batteryI 450 bridged between the windings of the repeatingcoil in the cord circuit (Fig. 4) through supervisory relay 445, out over the conductor 502 of the trunk line. to the final selector, through contact 542 of the sequence-switch thereof, and interrupterl 560, to earth. The supervisory lamp 413 before the operator will thus be caused to flash, indicating to her that the line for which connection has been asked is busy.

If the line tested is free, the test relay will complete a circuit from' battery 50G. through motor magnet 507 of the final selector sequeme-switch, to ay Contact 540 thereof', and front contact of the test relay 550, to earth. rlhis circuit is maintained until after the sequence-switch leaves the 0th position. and the local switch contact 510 is closed between the 9th and 11th positions, so that the sequence-switch instead of stopping at the 0th or busy-bach position, will run through to the lith position.

As soon as the sending operation com plated, and the Contact 401 closed at the seqi1ence-switch of the first selector` the line relay 520 at the finaly selector was excited by current from battery 504 derving through said line relay to trunk conductor 501, back through tlu` first selector and contact 401 of its sequence-switch, to the `around connection Vi752 of the repeating coil in the cord circuit. The line relay at thefinal selector being excited at the time its sequencereaches the 11th position, a circuit ai couipleted from bai .ery i i, through the motor magnet 507 of the sequence switch, Contact 50S thereof, front contact of the line relay 520, to earth: whereby the sequence.A switch will be moved to the 13th position. contact 510 being closed between the lith and llth positions.

In the 13th position the contacts' 52";0 and 537 are closed, connecting;r the poles of tbc ringing generator 550 to the line brushes :'31

55T associated with the final selector causes said relay to close a circuit from battery 50G, through motor magnet 507 of the sequenceswitch, contact 513 thereof, front contact of the sin'ieryisory relay 55T, to earth; whereby the seipience-switch is moved to the 14th or talking position. In this position the contacts .301 and 502 are closed, completing the talking circuit for the trunk line, through the repeating coil 570.

ln the 14 th or talking position of the final selector' seipience-switch, the supervisory relay .35T will receive current Vfrom the battery 571 bridged between two of the windings of tlic repeating coil, and will control at its front contact a path to ground from the trunk line conductor 502, thereby controlling the supervisory relay 415 in the cord circuit, which in turn controls the supervisory signal lamp 413 in the usual manner.

/Hsconncct/on.-When the operator receives the disconnect signal, indicated in the usual way by the lighting of the supervisory lamps 412 and 413, she takes down the connection by removing the answering plug 403 from the spring jack of the calling line. The cord relay 40.3 is thus'r'eleased and closes a circuit from battery 08, through the motor magnet 407 of the sequence-switch associated with the first selector, contact 472 thereof. and nach contact of cord relay to earth. The local contact 410 of the sequenceswitch being closed between the 8th and 18th positions thereof, said sequence-switch will be carried through to the 13th position, whereupon a circuit will be completed from battery 4708, through motor magnet 407, contact 473, back contact of supervisory relay 415, wire 474, contact 175 of the sequenceswitch. to earth. The sequence-switch will thus be carried to the 14th or return position in which a circuit will be completed from battery 42T, through power magnet 77 of thc smcctor. contact 470, back contact of the test relay,y to earth. The power disk 73, being ott-normal, its surface is nearer to the return driving roller Tet than to roller 75, so that said disk 4will be attracted into engagement with the roller T4, and the brushcarrying frame of the selector will be rofated back to normal position. As the cam .s0 in thc rcturn moven'ient closes the contact 415. a circuit is completed from battery 40o. through motor magnet 407 of the sequcncc witch, contact 432, Contact 82, swing nl., to earth, whereby the sequenceswitcli moved to its 15th position. `When the rotary brush larrier of the selector reaches its normal position the cam S0 opens contact and closes contact 83, completing a circuit from battery 408, through motor magnet 40T, contact 433 of the sequenceswitch. contact 83 closed oy the cam, to earth. The scquenceswitch of the first selector has sixteen positions, but the local contact 410 is closed between the 15th position and the 1st or normal position. so that the sequence-switch is carried through to its normal position. Upon leaving the 15th position the contact 470 is opened. breaking the circuit for the power magnet. and stop ping the rota'tion of the brush cahier frame. Both the first selector amt-iss sequence switch are nowzin;l normal position.

lVhcn the operator removed the plug from the springjack` and the serpicn'ce-switch of the first selector left its 8th or talking pos Sit-ion, Contact 401 was opened, thereby breaking the circuit of thc line relay 520 at the final selector, which was excited dnrinav the connection. The line relay :720 in ree covering establishes a circuit from battery 50G. through motor magnet 50T of the sequence-switch associated with the final selector, through contact 584 thereof, and hack ccntact ot' line relay 520, to earth. The sequenceswitch is therefore moved to the 15th position, in which contacts 561 and 562 are open, and contact 576 closed, the latter completing a circuit from battery 525, through the power magnet 77 of the final selector, contact 576 and back contact of the line relay 520, to earth. The brush carrier of the selector is now rotated back to normal position. as previously described with reference to the first selector. Vlien the cam 80 of the final selector in returning closes the contact a circuit is completed from the battery 500, through the motor magnet 507, contact 532 of the sequence-switch, contact 82 and spring 8l, to earth. The sequenceswitch is thus moved to the 16th position, and as the rotary element of the selector reaches its normal position cam 80 closes contact 83 of the final selector. and a circuitV is completed from battery 506, throughmotor magnet 50T, contact 5:53 of the sequenceswitch, contact 83 and spring 81, to earth; The sequence-switch of' the linal selector has seventeen positions, but as the local contact 510 is closed between the 16th and the 1st positions, the seqiience-switch upon leaving the 10th position, runs through to the 1st or normal position. All the apparatus of the system is now in the normal condition.

l claim:

1. The combination with a point-finder ha ving a series of contact points and a finder brush arranged to ,traverse said points in sequence, ot' a seriesv of keys adaptedto select corresponding points in said series, said keys being arranged in reverse order from the arrangement of the corresponding contact points in the series, selector mechanismrand means for operating said selector mechanism in conformity with the advance of'the finder brush beyond a selected point.

2. rl`he combination with a series of contact-points, of a finder adapted to traverse said points in sequence, a series of keys 

